History of the Peloponnesian War
Thucydides
Thucydides, Vol. 1-4. Smith, Charles Foster, translator. London and Cambridge, MA: Heinemann and Harvard University Press, 1919-1923.
for the favour which comes last, if conferred at the right moment, even though a small one, can cancel a greater offence.
Nor ought you to be tempted by their offer of a great naval alliance; for to refrain from wronging equals is a surer strength than to be carried away by present appearances and seek an advantage by incurring dangers.
"But we, since events have brought us under the rule which we ourselves proclaimed at Sparta, that each should discipline his own allies, now claim from you in return the same treatment—that you who were then aided by our vote should not injure us by yours.
Pay back like with like, determining that this is the supreme moment when assistance is cne truest friendship—opposition the worst hostility.